1. Field of the Invention
The present invention relates to a stage apparatus for measuring the position with a laser interferometer and to an exposure apparatus using the stage apparatus.
2. Description of the Related Art
A laser interferometer is used in exposure apparatus for measuring the position of a reticule stage where a reticule (original plate) is mounted and a wafer stage where a wafer (substrate) is mounted.
As an example of measuring the position with a laser interferometer, JP-A No. 319541/2002 discusses that a mirror is installed on the stage and the measuring light from the laser interferometer installed outside of the stage is irradiated onto the mirror. Then, the measuring light reflected by the mirror and the reference light led through a predetermined distance are allowed to interfere with each other. The position of the stage is measured by detecting this interfering light with a detector.
As mentioned above, in the case when the laser interferometer is used for measuring the position of the stage, the surface machining accuracy of the mirror and the mounting accuracy of the mirror become factors for measurement errors. The accuracy especially demanded for the stage apparatus in the exposure apparatus increases more and more, and a method to further decrease such a measurement error has increased in recent years.